The present invention is directed to electrolytic cells and more particularly to electrolytic cells containing a bipolar type electrode wherein the electrical current is transferred from the anolyte element to the cathode element within the cell in a fluid-tight manner. Although the present invention is particularly directed to bipolar cells, it is also useful in other types of electrolytic cell as will be apparent to those skilled in the art.
This invention is particularly well-suited for use in joining components of an electrolytic cell, e.g., anode and cathode plates, in a fluid-tight cell. The electrolysis of ionizable chemical salts, e.g., alkali metal halides, to yield useful basic staple chemical products, e.g., alkali metal hydroxides, halogen and hydrogen has long been practiced commercially. For example, such electrolysis has been carried out in diaphragm cells wherein there are two compartments separated by a porous diaphragm. One compartment contains the cathode and the other contains the anode with the electrolyte flowing from the anode compartment through the porous diaphragm into the cathode compartment completing the electrical circuit. A variation of such a two compartment cell, called a filter press arrangement, is one wherein a large number of cells are connected in series in a common housing. According to such a variation, the anode of one cell is connected electrically with a cathode of an adjacent cell with these cells being separated by a barrier serving to prevent the passage of electrolyte between the adjacent cells. Such a configuration is termed a bipolar electrode, and the series of cells is called a bipolar type filter press cell.
The provision of efficient electrode connections between the anode and cathode elements are components of adjacent cell units is important. However, obtaining efficient electrical contacts which are both compact, liquid and gas tight and capable of ready removal for maintenance of the other components of the cell can be a troublsome and elusive goal, particularly where there is a high density current flow within the electrolytic cell. There have been many patents directed to provision of various fluid-tight electrical contacts and connections for electrolytic cells. U.S. Pat. No. 3,429,799 to R. W. McWhorter is directed to a fluid-tight electrical connector for connecting anode and cathode electrodes 20 and 42. The electrical connector comprises a flanged cylindar 32 with an axial bore 24 therein and the bore contains a soft metal filler material which can be integrally joined to electrode 20 as by welding.
U.S. Pat. No. 3,788,966 issued to C. W. Stephenson III et al discribes an electrical connection for metal electrodes formed by coating each connector part with a layer of softer but compatible, nonoxidizing metal and joining the connector parts together by exersion of a shearing stress as the male and female bolt connector parts are joined together during the bolting procedure.
U.S. Pat. No. 3,824,173 to P. Bouy et al shows a ring 5 which electrically connects an anode plate 6 and cathode 8. Ring 5 carries resilient plate members (not numbered) on its inner and outer surfaces, and these plates electrically interconnect parts 1 and 2. Parts 1 and 2 in turn are electrically connected to the anode and cathode plates. The annular surface of the ring makes the electrical contact as opposed to the end surfaces (edges) of the substantially concentric spirals or rings of the electrical contact device of this invention.
U.S. Pat. No. 3,859,197 to P. Bouy et al is directed to bipolar electrodes wherein the two electrically active parts are apertured, and the electrical connection between is made through the electrical contact formed within a plurality of bonded, e.g., welded members produced by plating a metal which can be used cathodically with a film-forming metal, and then using the bonded members as part of a sealing partition separating the two electrically parts.
U.S. Pat. No. 3,915,833 to S. A. Michalek et al discribes an electrical contact made between the mating surfaces of the anode and cathode bosses by coating a valve metal anode boss with platinum and the ferrous metal or a nickel cathode boss surface with a soft metal such as copper. A soft metal gasket is placed between the bolt head and the pressure receiving shoulder of the boss through which the bolt passes.
U.S. Pat. No. 3,950,239 issued to W. E. Figueras shows a bipolar plate having an electrical connector which comprises a rod 9 which extends between an anode plate 1 and cathode plate 3. This rod is threadibly secured within cylindar 5 and is electrically connected to caps 5 and 10 which, in turn, are electrically connected with the anode and cathode plates.
U.S. Pat. No. 4,022,952 issued to D. H. Fritts utilizes a porous metal matrix 21 to electrically interconnect metal grids 22 and 23 and therefore electrically connect cathode 24 with anode 25. The porous metal matrix is filled with a heat sink material.
U.S. Pat. No. 4,026,782 to P. Bouy et al utilizes an elastically deformable sealing member resting against a diaphragm and arranged in the recess of an adjacent frame. The elastically deformable member is arranged in a housing made in the recess and has a shape, e.g., toroidal, retangular, etc., which is adapted to the configuration of the sealing member.
U.S. Pat. No. 4,085,027 issued to K. A. Pousch describes a fastener assembly 16 comprising a bolt member 74 and nut member 80 which are electrically conductive thereby providing an electrical connection between an anode plate 12 and cathode 14.
U.S. Pat. No. 4,105,529 issued to Gerald R. Pohto (inventor herein) illustrates a helicoil electrical connector aligned between conductive bars so that the longitudinal axis of the connector is parallel to the bars. No filler seal material is employed.
U.S. Pat. No. 4,108,752 issued to G. R. Pohto illustrates the use of a variety of electrical connectors for electrically connecting bipolar plates. The electrical connector (C) can be of a variety of configurations, e.g., in the form of a conductive strip having louvers extending outwardly of the planar faces of the strip (C) in alternating pairs outwardly of one face (louvers 50) or the other (louvers 52) of the conductor strip. As can be seen from FIG. 6, louvers 52 establish contact between parallel surfaces abutting thereto. FIG. 7 illustrates an undulate configuration for conductor strip (C) whereas FIG. 8 shows an askew helix-shaped electrical connector which is aligned between the plates so that its longitudinal axis is parallel to the face of the plates. This is in contrast to the contact device of the present invention wherein the longitudinal axis of the spiral (and the edges thereof) are perpendicular to the face of the electrode plate.
U.S. Pat. No. 4,116,805 issued to Ichisaka et al illustrates bipolar plates 2 and 3 electrically connected by a pin 19.
Also there is currently available on the market a gasket which applicant has utilized in the present invention to form an electrical contact. This gasket is marketed under the trade designation "SPIROTALLIC" and "FLEXITALLIC" and is of the spiral-wound type having a variety of filler materials, such as asbestos, PTFE (polytetrafluoroethylene) of both the solid and nonsintered variety. The "FLEXITALLIC" and "SPIROTALLIC" gaskets are advocated for use as a gasketing material in aircraft, diesel, gas and rocket engines; boiler feed, centrifugal, condensate, reciprocating and vacuum pumps; gauge and sight glasses; centrifugal and reciprocating compressors; high pressure and soot blowers; hydraulic and molding presses; gas and steam turbines; heat exchangers; high voltage power transformers; and all types of valves. In general, these gaskets are described as suitable for use in nonstandard joints and piping systems and pressure vessels.
Applicant has surprisingly discovered that these gasket materials of the spiral-wound spring variety are highly useful as fluid and air tight, electrical contact devices for conductively joining electrolytic cell anode and cathode plates particularly wherein there is a high current density electrolysis being conducted in such cells.